Yet it’s unclear how Iraq would enforce that rule, with an air force that has few planes and no fighter jets to protect its skies. That mission was previously handled by the U.S. military before American troops withdrew from Iraq last year.

While Iran may be sending the weapons as part of a region-wide battle for influence with the United States, the passivity of Iraq’s Shiite leaders may reflect more parochial concerns and the history of decades of minority Baathist domination, said Aram Nerguizian, a Middle East specialist at the Center for Strategic and International Studies.

He said it made sense that Iraq was hedging its bets at a time of dwindling hopes for Syrian peace and the possibility of another hostile Sunni state emerging one day on its borders.

‘‘It’s not just about helping Iran,’’ Nerguizian said. ‘‘This is also a byproduct of an Iraqi political environment where the leaders are far more worried about threats to Shiite rule.’’

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